1. Technical Field
Some aspects of the present invention relate to an optical device, an optical scanner, and an image forming apparatus manufactured using, for example, a micro electro mechanical system (MEMS) technology, and provided with a movable plate reciprocating around a shaft member.
2. Related Art
In the related art, as an optical device of this kind, there has been known a device provided with a magnetic field generating section and a scanning mirror supported on the both ends thereof with a support member so as to be able to perform angular displacement around a drive axis, wherein the scanning mirror is provided with a mirror surface formed on one surface thereof and a permanent magnet formed on the other surface, and the magnetic field generating section is disposed on the other surface side of the scanning mirror with a predetermined distance from the scanning mirror. Since in this optical device with the configuration described above the scanning mirror is driven separately and in the light-weight condition only with the thin film permanent magnet formed on the other surface thereof, it can easily be driven with relatively weak drive force even in the case in which the size of the scanning mirror is large (see, e.g., JP-A-6-82711).
Incidentally, since the distribution range of light entering the optical device is generally larger than the size of the movable plate having the light reflecting surface (the mirror), there have been the prominent cases in which the light enters the portion of the optical device other than the movable plate, in particular a drive section disposed in the vicinity of the movable plate and for generating electromagnetic force in a space between the drive section and a ferromagnetic member provided to the movable plate to thereby swing the movable plate. In this case, the light entering the drive section does not move even when the movable plate is driven (to scan the light), and is therefore always reflected to the same position. As a result, there has been a possibility that the light entering the drive section appears as so-called stray light in, for example, the range of the reflected light by the movable plate, other optical devices including the range of the reflected light, mirrors, a screen (including a screen illuminated via the other optical devices, the mirrors, and so on). It should be noted that since a coil made of a metal material with high reflectance, for example, is often used as the drive section, it is possible to provide black coating on the surface of the coil in order for preventing the reflected light. However, according to this method, since the stray light itself still appears although the intensity of the stray light can be reduced, the method cannot be called a radical solution.